Such a transport mechanism is used for example on a Wire Bonder to transport substrates. A Wire Bonder is a machine with which semiconductor chips are wired by means of pressure, ultrasound and heat after they have been mounted onto a substrate. The transport mechanism comprises two guide rails, at least one clamping device moveable back and forth along the guide rails and at least one holding device. The moveable clamping device serves to transport the substrate in transport direction along the guide rails to the bonding station and away from the bonding station. The holding device serves to hold the substrate between the transport phases. The holding device is for example a rigidly arranged clamping device or a roller resting on the substrate that presses the substrate against the guide rail. The roller contains a special bearing that only allows the roller to turn in one rotational direction and blocks the roller in the opposite rotational direction. The solution with the roller is comparatively expensive and has the disadvantage that movement of the substrate in transport direction is always possible as the roller only makes movement impossible opposite to the transport direction. The rigidly arranged clamping device has the disadvantage that the clamp jaw has to be moved in order to clamp the substrate. The moved clamp jaw is a moved mass that, on impacting on the substrate, transmits a certain energy to the substrate and jolts the substrate. Especially with thin substrates—there are substrates that are only 50 micrometers thick—the vibrations can cause the bond wires of already wired semiconductor chips to deform and, under certain circumstances, neighbouring bond wires to come into contact with each other and produce an electrical short-circuit.
Transport mechanisms with fixed and/or moveable clamping devices are known from EP 330'831, CH 679'878 and CH 689'188.